System file checker

System File Checker verifies the integrity of your system files. After scanning for altered files, it offers to restore corrupted files. If a file is found to be corrupt, you will be prompted to restore the original file. By clicking Settings, System File Checker can also be configured to notify you of changed and deleted files. If you choose to restore the file, System File Checker attempts to extract the file from your original Windows 98 installation source.

System File Checker (Sfc.exe) helps you do two things:

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 Open system file checker

The following dialog box appears:

From here, as can be seen, there are two options, either to scan for altered files or to extract a file from the installation disk.

Scanning for altered files

System File Checker scans the system using a default baseline contained in a file named Default.sfc. This file is copied from the Windows 98 installation source and contains the following information about each system file:

Cyclical Redundancy Check (CRC)

This is a checksum added to a file entry whenever a file is written to disk. This data is used to see if the file has changed.

Date, time, size, and version information  

If System File Checker determines a change in date, time, size, or version, it considers the file to be changed.

In System File Checker:

Update the verification information

Choose this option when you have updated a system file without running System File Checker. For example, you may have installed new software or an update. This will update Default.sfc and the next time System File Checker is run, the new information about the file will be used.

Restore file

Choose this option if you are certain the file needs to be restored from the original. You must specify the source location of the file to restore and where to save the new copy of the file. The destination field will normally be filled out automatically for you by Windows and the source (assuming it is a Windows system file) will normally be the \WIN98 folder on the Windows CD-ROM. You are also prompted to back up the existing file to the \Windows\Helpdesk\SFC folder. Choose to back up the file in case there are problems using the new file.


Choose this option to skip the file. The next time System File Checker is run, this file will cause the File Changed dialog box to appear because it was not added to Default.sfc and it was not restored.

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Customising System File Checker scan options

You can customise the criteria that System File Checker uses to check files.

From the main System File Checker opening window:

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To extract a specific system file

In System File Checker:

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was last reviewed August 17, 2002